This invention relates to a parts recognizing device and more particularly to an improved optical parts recognizing device for use with component mounting apparatus.
There are a wide variety of devices commonly referred to as "chip mounters" that are employed to pick up small components at one location and mount them in an accurate position on an article such as a printed circuit board or the like. These devices are particularly useful and frequently employ pick-up nozzles such as vacuum operated pick-up nozzles for selecting the components and positioning them.
In connection with this type of apparatus, normally some optical device is employed for either or both of the purposes of identifying the component that has been picked up and/or determining the orientation of the component relative to the pick-up device. Regardless of which type of recognition is employed or even if both recognitions are employed, it is generally the practice to utilize for recognition purposes an electronic camera such as a capacitor couple device (CCD) and a light source. The light source illuminates the component that is picked up so that the camera can take an image of it.
As is noted above, this recognition can serve one or both of two purposes. First, the camera and associated computer control may be employed to recognize and assure that the correct component has been picked up by the pick-up device from the feed station. The other purpose is to determine the orientation of the component relative to the pick-up device. The reason for this is that it is difficult if not impossible to insure that each component will be picked up in exactly the same orientation. Therefore, a variety of methods have been employed for determining if the component as picked up is offset relative to the pick-up device so that corrections may be made in the location of the pick-up device relative to the circuit board prior to assembly.
Normally it has been the practice to perform the recognition in a specific location on the apparatus and in this recognition area there is provided both the light source and the electronic camera. However, the use of a single type of light source and a single electronic camera can present some problems because the components which are positioned and mounted on the circuit boardscan have different natures that require different types of recognition. For example, if the light source is mounted on the same side of the pick-up device as the camera, then the camera will recognize the component by directly seeing its image. With some forms of components this is acceptable. However, with other types of components this may not be an acceptable recognition method. For example, if the component has a plurality of lead wires which must be connected to the circuit board and these are disposed adjacent the side to be mounted, then the lead wires will give a reflection from the light source that can make it difficult to determine both the type of component and the location of the lead wires.
On the other hand, if the light source is disposed on the opposite side of the component from the electronic camera so that the camera will sense the shadow of the object, then other difficulties can be encountered. If the part is particularly small, the pick-up device itself may obscure the light and may make it difficult to both identify and determine the location of the component.
In order to ensure that the apparatus is capable of handling a wide variety of components and recognizing both the component and/or its orientation, it has, therefore, been necessary previously to provide a number of different recognition stations some of which use direct illumination and some of which use back lighted illumination in order to recognize and orient the component. Obviously, this adds considerably to the cost of the mechanism. In addition to this, it can also have the effect of slowing down or retarding the speed of operation, also an objectionable result.
It is, therefore, a principal object of this invention to provide an improved parts recognition mechanism for a mounting machine.
It is a further object of this invention to provide an optical parts recognizing system for a mounting machine that will permit either direct or back lighting for recognition purposes in the same station.
It is a further object of this invention to provide an improved recognition arrangement for a mounting machine wherein the use of separate stations and separate recognition modes can be avoided.
It is a still further object of this invention to provide an improved component recognition system for a mounting machine wherein alternate light sources can be employed in the same station and without necessitating duplication of components.
It is a further object of this invention to provide an improved optical recognition arrangement for a mounting machine that permits recognition by either direct or back lighting in a single station and with a minimum number of light sources and a single electronic camera.